Laser light has gained acceptance as a controllable light source not only in scientific research but also in many fields of everyday life. This is primarily due to the fact that a laser provides a monochromatic light source with coherent radiation which can be focused very well due to the small divergence. The use of lasers has become increasingly common not only in the field of telecommunications and entertainment electronics but also for treating materials and for medical purposes. In the latter field, it has been of decisive importance that a laser is an instrument permitting, on the one hand, the use of high-energy radiation for heating tissue in a precisely localized manner and for destroying endogenic calculi and, on the other hand, the use of monochromatic radiation for selectively stimulating photochemical processes. In this respect, a distinction is made between lasers used as an aid in doing a major operation and the use of lasers as an actual therapeutic method.
In the field of surgery, lasers are primarily used because of their haemostatic effect, the possibility of precise handling, and the reduction of the number of instruments in the operating field. Contact-free removal of tissue and minimum traumatizing of the surrounding tissue by force-free treatment of the tissue are essential advantages achieved by the use of a laser.
Another field of application of laser technology in medicine is the treatment of body surfaces. Lasers are here used for removing or coagulating skin and cutaneous appendages on the one hand and for treating intracutaneous vascular modifications and malformations on the other. Cutaneous tumors, for example, are nowadays preferably coagulated by means of an Nd:YAG laser or, alternatively, removed by means of a CO2 laser. Non-malignant pigmentary anomalies are treated with alexandrite or argon lasers. Alexandrite lasers and pulsed Nd:YAG lasers are also used for removing tattoos and for the purpose of depilation.
Also in the field of endoscopy, lasers have become indispensable. Laser light conducted via light-guides to the location of application can here lead to a further reduction of size and thus to a higher flexibility of endoscopic operations. Due to the further development and primarily due to the miniaturization of the instruments as well as the refinement of flexible endoscopes, several new fields of application, in which conventional operations had to be performed up to now or in which the application of minimal-invasive therapies has been impossible up to now, have been opened up for the use of laser technology.
The increasing number of fields of application of laser technology in medicine resulted in the development of technically more and more progressive laser designs and corresponding system concepts, which facilitated and improved the handling of laser systems and which, in turn, opened up new fields of use.
This development of medical laser systems now continues and leads even to “intelligent” systems. German Patent Publication DE4025851 describes such an “intelligent” laser system in which reemitted radiation produced during the treatment of material by means of laser light is transmitted to a detector via a transmission system for the laser light. The detector determines the intensity of the reemitted radiation. Such a laser system can successfully be used for minimizing unintentional tissue damage, since the laser power is controlled automatically via the detection of the intensity of the reemitted radiation.
In this connection, the use of flexible, optical transmission systems for the laser radiation produced is of substantial importance, since, for applying the laser radiation to the tissue to be treated, the distance between the laser unit output and the patient has to be bridged. Hence, medical laser systems are typically composed of a stationary or mobile laser unit, beam guiding means, optical terminals, and accessories for special medical applications. For the transmission of visible laser light and the adjoining spectral regions of approx. 0.3–2.1 μm, flexible glass or silica fibers are used. In the spectral regions 0.19–0.3 μm (Eximer laser) and 3–10 μm (erbium and CO2 laser), special light-guides or articulated arms with mirrors are used. Light-guides have to fulfill particularly high demands when pulsed, high-energy laser radiation is to be transmitted for the purpose of laser lithotripsy. Good handling properties and a high flexibility of these transmission systems is of decisive importance with regard to the use of the laser systems.
In the case of all application possibilities of lasers in the field of medicine, the handling properties of the laser radiation are of essential importance. Flexibility, ergonomics, and functionality are in this connection as important as safety, reliability, and precision. These are the factors that determine to a decisive extent whether the advantages of a laser can actually be utilized when carrying out the treatment in question.
In this connection, it is of essential importance how the hand-piece of a laser system, which is coupled to the laser unit output by means of an articulated arm with mirrors or by a flexible glass fiber, is user-friendly usable and operable. This includes functionalities, such as, for example, a continuous adjustment of the spot size of the laser focus. Up to now, it has been necessary to manually readjust the laser power at the laser unit after an adjustment of the spot size. More recent generations of laser systems allow an adaptation of the laser power through remote control. For this purpose, either additional electric cables from the hand-piece to the laser or RF radio transmission is/are used for transmitting data from a laser hand-piece to the laser unit. Another possibility is infrared transmission, which is either directed or diffuse. Each of these three transmission possibilities has certain specific drawbacks with respect to handiness, power consumption and effectiveness of the method, or they lead to problems as far as a worldwide approval of the laser system is concerned.